While Microsoft's lead in the desktop computer operating system market seems unassailable, it has not fared nearly so well in the palmtop arena. After several false starts, the firm's Pocket PC (formerly Windows CE) operating system has finally got off the blocks, but just as it seems to be gaining ground on frontrunner Palm OS, a new contender has arrived.

And it is the same competitor that is snapping boisterously at the heels of Microsoft Windows in the desktop department - Linux.

If you haven't heard of Linux, the main thing to know is that it is Windows for the wise and wealthless: an operating system designed by enthusiasts from the ground up and distributed freely to anyone who wishes to download the data files or obtain them on CD-Rom. It looks similar to Windows, works in much the same way on the surface, but underneath - and here is the rub, according to its proponents - it is much more reliable.

At the moment, Linux appeals mainly to computer hobbyists with the time and inclination to make it work with existing hardware setups - Linux's support for peripherals and applications being limited - and corporations whose IT budgets are big enough to allow them to tailor it to match their needs precisely.

That, perhaps, helps explain why Sharp has chosen the leftfield operating system to power its latest personal digital assistant (PDA). Big businesses buy an awful lot of these things, and some of today's most popular gadgets grew from a groundswell of enthusiasts.

The Zaurus is a good-looking device - the shiny central control pad contrasts well with the steel-effect look of the case - but the unit is lengthier than its contemporaries. The reason for this is found under the main control panel: a quick flick of the thumb pulls it down to reveal a minuscule Qwerty keyboard, set out to form a slight arc.

Naturally, the buttons are small, but the keyboard is surprisingly elegant in use: a two-thumb tapping approach soon pays entry-speed dividends.

The keyboard complements rather than replaces traditional palmtop entry methods, so if you prefer character/handwriting recognition or stylus-pecking at an on-screen keyboard, the Zaurus will not disappoint.

Powering up the device for the first time engenders a decidedly dated feeling. The screen fills with a scrolling list of command-line instructions. It's not unlike watching an early Dos-based computer going through its startup procedure. The machine even declares that it is 'booting'.

After this you could be forgiven for thinking the Zaurus was a Pocket PC palmtop. Colourful icons and tabbed headers make navigation an intuitive affair. Want to add a contact's details? Click the Address Book icon. Need to calculate some figures? Use the Calculator icon.

The screen is fantastic. It looks far better than its 240x320-pixel resolution would suggest, and adjustable backlighting solves the problem of dark conditions. However, while the touch-sensitive surface is responsive to stylus pecks and strokes, a jog-dial would have aided navigation. Moreover, right-handed users will find that the thumb of their holding hand could obscure the unit's infrared transmitter - a thoughtless piece of design.

In terms of expansion, the Zaurus is well-equipped. The machine's impressive 64MB memory can be augmented by the insertion of SD memory cards or CompactFlash add-ons. And do not think the Linux operating system precludes Windows users from making the most of the Zaurus: Sharp supplies a PC docking cradle and synchronisation software, which both work well.

It is difficult not to like the Zaurus. The machine is powerful, well-designed and reasonably priced. Linux is very much an unknown quantity in PDA terms, but such is the community spirit that software support is all but guaranteed.

Specifications:

Price: £449.99 (inc VAT)
Contact:Sharp: 0800 138 8879
www.sharp.co.uk